Conventionally, an ejector-type refrigeration cycle that is a vapor compression-type refrigeration cycle including an ejector as a refrigerant depressurizing device is known. For example, in Patent Document 1, an ejector-type refrigeration cycle is disclosed, which includes a gas-liquid separator that separates gas and liquid of refrigerant flowing out of an ejector. The liquid-phase refrigerant separated by the gas-liquid separator flows into an evaporator while the gas-phase refrigerant separated by the gas-liquid separator is drawn into a compressor.
More specifically, in the ejector-type refrigeration cycle of Patent Document 1, refrigerant flowing downstream of the evaporator is drawn through a refrigerant suction port of the ejector by a suction action (pump action) of high-speed ejection refrigerant ejected from a nozzle portion of the ejector. Mixture refrigerant of the ejection refrigerant and the suction refrigerant is pressurized in a diffuser portion (pressurizing portion) and flows into the gas-liquid separator.
Accordingly, in the ejector-type refrigeration cycle of Patent Document 1, a refrigerant pressure in the gas-liquid separator that corresponds to a pressure of refrigerant drawn into the compressor can be increased to be higher than an evaporation pressure of refrigerant in the evaporator. Hence, power consumption can be reduced and coefficient of performance (COP) can be improved, as compared to a normal refrigeration cycle device in which a pressure of refrigerant drawn into a compressor is approximately equal to an evaporation pressure of refrigerant in an evaporator.
In a configuration like the ejector-type refrigeration cycle of Patent Document 1, the refrigerant on a downstream side of the evaporator is drawn by the suction action of the ejection refrigerant ejected from the nozzle portion of the ejector. Thus, when a flow rate of the ejection refrigerant is reduced, a degree of reduction in suction capacity to draw the refrigerant on the downstream side of the evaporator through the refrigerant suction port is likely to be larger than a degree of reduction in flow rate of the ejection refrigerant.
Hence, when the flow rate of the ejection refrigerant in, for example, a low-load operation in which a thermal load on the cycle is reduced, the suction capacity of the ejector may decrease largely, and the refrigerant may not flow into the evaporator accordingly. Therefore, in the low-load operation, a cooling target fluid may not be cooled sufficiently in the evaporator.